P732: TH17/TREG IMBALANCE IN LOW RISK MDS PATIENTS
Authors: M. Boada, N. Trias, A. Brugnini, C. Guillermo, S. Grille
Journal: HemaSphere (2022)

Background: Myelodysplastic Syndromes (MDS) are a heterogeneous group of clonal haematopoietic stem/progenitor cells (HSPC) disorders characterized by ineffective haematopoiesis, peripheral cytopenia, and risk of acute myeloid leukemia (AML). MDS pathogenesis is complex and depends on the interaction between HSPC and microenvironment. Many studies have highlighted the role of different immune cells in immune dysregulation leading to pathogenesis of MDS and progression of disease to AML. Immune response differs between risk groups favouring a pro-inflammatory profile in low risk, whereas in high-risk patients there is a trend towards immunosuppressive environment. Regulatory T cells (TRegs) and T helper 17 cells (Th17) are CD4 T cell functional subsets and their balance (TH17/TReg) is essential for maintaining immune haemostasis Aims: To study T cell subsets and cytokines plasma levels in low risk MDS patients and healthy controls. Methods: This is a case control study conducted in Hospital de Clinicas Montevideo, Uruguay. Patient inclusion criteria were Low Risk MDS (R-IPSS <4.5) and control group were healthy blood donors. We assessed peripheral blood T cell subsets by multiparametric flow cytometry using the following monoclonal antibodies: CD45, CD3, CD4, CD8, CXCR3, CCR6, CCR4, CD25 and CD127. Subpopulations were defined as reported by Maecker et al (1). Cytokine’s plasma levels were determined by Cytometric Bead Array (BD). We studied pro-inflammatory, TH1, TH2 and TH17 cytokines (IL-2, IL-4, IL-6, IL-10, INFg, TNFa, and IL-17). The protocol was authorized by the Ethics Committee of the institution and all subjects signed an informed consent. Results: We included 24 MDS patients and 19 controls with a median age of 68.5 (47-78) and 48 (32-55) years respectively. Male:Female ratio was 1.3:1 in controls and 0.9:1 in patients (p˃0.05). According to R-IPSS we included 13 (30.2%) Very Low Risk, 11 (25.2%) Low risk and 19 (44.2%) Intermediate patients. MDS patients showed lower proportion of Treg cells (p<0.001) and higher TH17/Treg ratio (p<0.001) than controls (Figure 1). There were no statistical differences in total T CD4+ cells and TH1/TH2 ratio. IL-2, IL-6 and IFN-γ levels were higher in patients than controls. Median levels of IL-2 were 0.2 (0.1-4.5) pg/mL in patients and 0.1 (0.0-2.6) pg/mL in controls, p=0.002. Median levels of IL-6 were 9.4 (0.5-10.5) pg/mL in patients and 0.5 (0.2-2.9) pg/mL in controls, p=0.001. Median levels of IFN-γ were 2.2 (1.1-3.3) pg/mL in patients and 0.1 (0.0-2.6) pg/mL in controls, p=0.003. There was no statistical difference in IL-4, IL-10, TNFa, and IL-17A between groups. Image:Summary/Conclusion: Our results showed that TH17/Treg balance is impaired, revealing a predominant proinflammatory state in in MDS Low risk patients. This occurs in concordance with elevated pro-inflammatory cytokines (IL-2, IL-6 and IFN-γ). These findings agree with previous reports that evidenced TH17/Treg ratio was higher in low risk MDS patients when compared with high risk. However, those studies highlighted the importance of TReg expansion and its prognostic impact in high risk. Evidence comparing TH17/TReg balance between low risk MDS patients and controls is scant. We believe that these results support the importance of a pro-inflammatory response in low-risk patients. 1. Maecker HT et al. Standardizing immunophenotyping for the Human Immunology Project. Nature Reviews Immunology. 2012;12(3):191-200. doi:10.1038/nri3158